The invention relates to a fluid energy machine, in particular for an exhaust gas turbocharger of a motor vehicle internal combustion engine.
EP 1 394 359 A1 discloses a turbine for an exhaust gas turbocharger, wherein the turbine is in the form of a so-called mixed flow turbine. The turbine comprises a turbine casing which includes a housing space in which a turbine wheel mounted on a shaft is rotatably supported. Furthermore, the turbine casing comprises at least one inlet flow passage through which the exhaust gas may flow. The exhaust gas is supplied to the inlet flow passage via a supply duct which is fluidly connected with the passage for directing the exhaust gas onto the turbine wheel in the housing space.
The turbine is referred to as a mixed flow turbine because the exhaust gas which is directed via the supply duct and the inlet flow passage into the housing space and onto the turbine wheel has a flow direction which extends at an angle relative to the axial as well as to the radial direction of the turbine. This means that the exhaust gas flows into the turbine wheel at an angle.
In the inlet passage, a guide element is positioned upstream of the turbine wheel, by means of which the flow of exhaust gas may be redirected. In the arrangement shown, the guide element is fixed relative to the turbine casing.
Furthermore, from series production of exhaust gas turbochargers it is known that variable turbine geometries for radial turbines of exhaust gas turbochargers are employed. Herein, the guide element arranged in the inlet passage may be pivoted about an axis of rotation which extends at least essentially in the axial direction relative to the turbine casing.
It was found that such variable turbine geometry cannot be applied easily to a mixed flow turbine, because jamming of the guide element may occur. The implementation of particularly large gap dimensions for preventing such jamming would result in an only low-efficiency operation of the turbine, because exhaust gas would bypass the guide element and thus flow to the turbine wheel in the housing space not properly oriented.
It is therefore the principal object of the present invention to provide a fluid energy machine with an inclined inlet passage including adjustable vane elements, which can be operated efficiently and reliably and which provides for a compact design.